Documentation/core-api/dma-isa-lpc.rst

12 ------------------------
16 	#include <linux/dma-mapping.h>
20 bus addresses (see Documentation/core-api/dma-api.rst for details).
28 -----------------
37 The DMA-able address space is the lowest 16 MB of _physical_ memory.
39 or 128 KiB depending on which channel you use).
45 allocate the memory during boot-up it's a good idea to also pass
52 -------------------
66 --------
68 A normal ISA DMA controller has 8 channels. The lower four are for
69 8-bit transfers and the upper four are for 16-bit transfers.
72 channel 4 is used to give DMA access for the second controller (0-3).
73 This means that of the four 16-bits channels only three are usable.)
80 The ability to use 16-bit or 8-bit transfers is _not_ up to you as a
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96 controller that is used for the non-atomic operations. As long as you
105 be 16-bit aligned for 16-bit transfers) and how many bytes to
109 The final step is enabling the DMA channel and releasing the DMA
113 the channel again. You should also check get_dma_residue() to make
124 	set_dma_mode(channel, DMA_MODE_WRITE);
125 	set_dma_addr(channel, phys_addr);
126 	set_dma_count(channel, num_bytes);
128 	dma_enable(channel);
136 	dma_disable(channel);
138 	residue = dma_get_residue(channel);
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